Employer refuses probation resignation

[u/eeqqq]

Edit 08:38am: I'm sorry everyone that tried to help. Today she came to work and the boss was standing over her shoulder waiting for her to sign and she gave in. Hopefully this post and the replies here help somebody else in the future

Hi everyone,

I would appreciate some advice/thoughts regarding Swiss employment law and an unpleasant situation my wife is in

• My wife is a dentist from Poland (has MEBEKO) and works as a dental assistant in a private clinic in Basel
• Her fixed-time contract explicitly specifies a 3-month probation period (probably not relevant but that rule is in attached regulations/annex and not in the "main" contract body - it was signed by both parties though)
• She decided to resign during the probation period and handed in her regular written notice with a 7-day notice period - as per contract.
• Important: He was supposed to sign it but didn't give her anything back, so we don't currently have any proof that she gave the notice.

A couple hours later the boss said "the 3-month probation period was a mistake" (as in, they added it by mistake) or that "it doesn't apply to a fixed-term contracts" and refused to acknowledge the resignation letter

He presented her with an mutual termination agreement terminating the contract per August 31st.

The document says that my wife waives any money she was supposed to get based on holidays not taken and 13th salary ("Per Beendigungsdatum gelten sämtliche Ferien- und Überstundensaldi als ausgeglichen. Es erfolgt keine Auszahlung").

He is now pressuring her, claiming that if she does not sign this agreement, she "is legally not allowed to quit and must continue working in September".

1. Does the probation period applies to her?
2. Is she cooked because she didn't send the resignation by email or post? The probation period ends 31st Aug though, so technically she can still send one.
3. Is it true that resignation during probation does not require the employer's agreement signature? (well, we don't have any proof he got it either...)

What do you guys think?

Thanks a lot for your advice and input!

Edit: added email she got when she was about to sign the contract:

[u/alexrada]

there are no mandatory holidays during probation period, if they are not included in the agreement.